Brake failure warning system

ABSTRACT

A brake failure warning light that monitors a number of functions. If one of the functions is out of tolerance, the light will be energized. By inclusion of an oscillating signal and control logic, the light will flash. Also, a bimetal switch could be used to periodically interrupt energy being delivered to the light. A self test is incorporated to determine if the warning light is operating properly. The functions being monitored by the warning light are the brake master cylinder fluid levels, the electronic control unit for an adaptive braking system and the braking pressure differential in a split system.

United States Patent 91 Houseman 1 Jan. 16, 1973 BRAKE FAILURE WARNINGSYSTEM Primary Examiner-Alvin H. Waring [75] Inventor. Pan's HousemansbuthBend mi Attorney-William N. Antonis and Flame, Hartz,

. f Smith8LThomps0n [73] Assigneez The Bendix Corporation 22 Filed:Sept. 30, 1970 [57] ABSTRACT Appl. No.: 76,932

References Cited UNITED STATES PATENTS 2/1956 l-losford ..340/27 NA11/1970 Hambre ..340/27 X A brake failure warning light that monitors anumber of functions. If one of the functions is out of tolerance, thelight will be energized. By inclusion of an oscillating signal andcontrol logic, the light will flash. Also, a bimetal switch could beused to periodically interrupt energy being delivered to the light. Aself test is incorporated to determine if the warning light is operatingproperly. The functions being monitored by the warning light are thebrake master cylinder fluid levels, the electronic control unit for anadaptive braking system and the braking pressure differential in a splitsystem.

3 Claims, 5 Drawing Figures MULTIVIBRATOR PATENTEDJAN 16 I975 3.711.827

sum 1 M 2 T '-38 L \MULTIVIBRATOR a .START RUN INVENTOR PAUL S. HOUSEMANATTORN EYS BRAKE FAILURE WARNING SYSTEM BACKGROUND OF THE INVENTION Astodays automobiles become more complex, additional warning indicationdevices are required to monitor failure or out-of-tolerance conditionswithin the automotive vehicle. The early automobiles required very few,if any, indicating devices. As time and technology progressed, a fewsimple warning or indication devices were included. Some of these simpledevices include fuel gauge, temperature indicator, generator charge, oilpressure, etc. With increased technology, the automobile of today hasbecome a very complicated machine. With the increase in complexity,there is a simultaneous increase in the number of possible failures.Hence, it becomes increasingly important for the automobile manufacturerto include warning devices that could monitor the various possiblefailures or out-oftolerance conditions that could conceivably result inpersonal or property damage by the vehicle operator. If a separatewarning indication device had to used for each monitored condition, analmost endless number of warning devices would be required. To eliminatethe need for such a large number of warning devices, it is verydesirable if one warning device can be used to monitor numerousconditions within the automotive vehicle.

Referring more specifically to the braking system of v the automotivevehicle, it is desirable to indicate more than whether or not the brakesare, or are not, opera- ,ble. Suppose there is an instantaneous brakefailure while a person is driving down a busy street. This instantaneousbrake failure could result in serious injury or property damage topersons or property involved in a subsequent automotive accident. Thereare economic devices today that can indicate to the operator of thevehicle whether his brake fluid is low, whether he has a pressuredifferential between his front and rear brakes during a brakeapplication, or, with the coming acceptance of adaptive braking, whetherthe electronic control unit of the adaptive braking system isfunctioning properly. Low fluid level indication is a warning ofpotential future failure. Differential pressure is an indication ofpartial, not total, brake failure. Adaptive braking is a systemmalfunction. These are just a few of the more desirable parameters thatmay be monitored on future automotive vehicles.

SUMMARY OF THE INVENTION It is an object of the present invention to usea single warning device to monitor a number of out-oftoleranceconditions.

It is a further object of the present invention to monitor various brakeparameters and give a single warning if one or more of the brakeparameters is out of tolerance.

It is a still further object of the present invention to provide aflashing indicator light when one of the parameters in the brakingsystem of an automotive vehicle is out of tolerance.

It is an even further object of the present invention to monitor thefluid levels, pressure differential and electronic control unit in abraking system of an automotive vehicle with a warning light beingflashed if one of the monitored conditions is out of tolerance.

It is another object of the present invention to provide a self test forthe brake failure indication system.

It is still another object of the present invention to show variousembodiments that can be economically manufactured whereinone warningdevice will monitor a number of out-of-tolerance conditions in thebraking system.

BRAKING DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustrative blockdiagram of one embodiment of the brake failure warning system.

FIG. 2 is an illustrative block diagram of a second embodiment of thebrake failure warning system.

FIG. 3 is an illustrative blockdiagram of a third embodiment of thebrake failure warning system.

FIG. 4 is an illustrative block diagram of a fourth embodiment of thebrake failure warning system.

FIG. 5 is a detailed electrical schematic of a brake failure warningsystem that is functionally the same as FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the firstembodiment shown in FIG. 1, the brake failure warning system, indicatedgenerally by reference numeral 10, is operated from the automotivevehicle battery voltage +V. A double pole, double throw switch 12 isprovided by the ignition of the automotive vehicle so that wiper arm 14is continuously energized when the automotive vehicle is in the START orRUN position. Wiper arm 16 is energized only when the ignition is in theSTART position. Neither wiper arm 14 nor 16 will be energized when theignition switch 12 is OFF (not shown). However, it could be possible forthe voltage to be continuously applied to the brake failure warningsystem with a minimum amount of current drain.

In referring to the details of the circuit shown in FIG. 1, switches 18and 20 continuously monitor the fluid level in a slip braking system. Ifthe fluid level in one reservoir of a dual master cylinder is low, thenone of the fluid level switches 18 or 20 will open. If the fluid levelin both chambers of the master cylinder is low, then both fluid levelswitches 18 and 20 will open. For details of a fluid level indicatingswitch that can be used in the present invention, see U. S. Pat.application Ser. No. 689,088, filed on Dec. 8, 1967 and having a commonassignee as the present invention. Switch 22 is a pressure differentialswitch that is normally closed. However, if a pressure differentialexists between the front and rear brakes in a slipbraking system duringa A brake application, then switch 22 will open. Alternatively, anormally open switch can be used if connected in the appropriate manner.Typical examples of pressure switches for use in split braking systemscan be found in U. S. application Ser. No. 832,162, filed on June ll,1969; U. S. application Ser. No. 42,1l0, filed on June I, 1970; and U.S. application Ser. No. 670, filed on Jan. 5, 1970. Switch 24, which isa normally open switch, closes when there is a failure in the electroniccontrol unit of an adaptive braking system (not shown). A typicalexample of a failure indication switch for an adaptive braking system isshown in U. S. application Ser. No. 785,664, filed on Dec. 20, 1968.

One side of the fluid level switches 18 and 20, the pressuredifferential switch 22, and the electronic control unit switch 24 isconnected to ground. The other side of the switches 18, 20 and 22 and 24form separate inputs 26, 28 30 and 32 to OR gate 34. The input 32 isinverted by inverter 36 so that OR gate 34 will only have ground inputwhen the switches 18, 20, 22 and 24 are in their normal condition. Ifwhile the vehicle ignition switch 12 is in the RUN position, one of theswitches 18, 20, 22 or 24 is changed from its normal position as shownin FIG. 1, then OR gate 34 would give a positive voltage output. Sinceswitch 18, 20, 22 or 24 would change from its normal position only if anout-ofltolerance condition exists, then an output from OR gate 34indicates that the braking system is not functioning properly.

This output from OR gate 34 could be used directly to drive a warningdevice. However, to flash an indicator light at a given frequency,multi-vibrator 38 and NAND gate 40 have been included. The multivibrator38 which may give an output anywhere from 0.1 to Hertz is utilized toalternately flash an indicator light 42. Normal operating frequency ofmulti-vibrator 38 will be one to 2 cycles per second. The output ofmultivibrator 38 and the output of OR gate 34 are fed into NAND gate 40to alternately close and open a conduction path to ground for indicatorlight 40 when an outof-tolerance condition has changed the position ofone of the switches 18, 20, 22 or 24. Though not shown, the power usedto operate OR gate 34, multi-vibrator 38, and NAND gate 40 is suppliedby the vehicle battery +V when the ignition switch 12 is in the START orRUN position. Though power could be applied when the ignition switch 12is in the OFF position. without lighting the indicating light 42, thiscould cause a small current drain on the vehicle battery and, therefore,is not included in the preferred embodiment. Wiper arm 14 completes thecircuit by connecting indicator lamp 42 to the vehicle battery +V sothat the lamp 42 will light when a ground output is received from NANDgate 40 and the ignition switch 12 is in the START or RUN position.

Also provided in FIG. 1 is a means to self test the brake failurewarning system 10. Resistor 44 which is connected on one end to one ofthe inputs 26, 28 or 30 and, on the other end to a start contact forwiper arm 16. Hence, the battery voltage +V is connected throughresistor 44 to one of the inputs of OR gate 34 so that indicator lamp 42will flash during the starting of the automotive vehicle. This testfeature will tell the operator of the vehicle if lamp 42 is burned outor if OR gate 34, NAND gate 40, or multi-vibrator 38 is not functioningproperly.

It should be obvious to those skilled in the art that the four functionsmonitored by switches 18, 20, 22 and 24 are just a few of an almostendless list of functions in a braking system that could be monitored.It is also clearly obvious to those skilled in the art that the warningindication system as shown in FIG. 10 can be used to monitor any type ofunrelated tolerance condition and utilize a single warning device.

Referring now to FIG. 2, like components, as shown in FIG. 1, will berepresented by the same reference numerals increased by 100. Thedifference between FIGS. 1 and 2 resides in the bimetal switch 46 ofFIG. 2 which replaces multi-vibrator 38 and NAND gate 40 shown inFIG. 1. Therefore, when the ignition switch 12 of the automotive vehicleis in either the START or the RUN condition so that a voltage is appliedto one side of indicator lamp 142, and the output of NOR gate 134 is ata ground potential, current will flow through indicator lamp 142 andbimetal switch 46 thereby causing indicator lamp 142 to glow. However,the current through bimetal switch 46 will cause the two metals 48 and50 to expand at different rates thereby breaking contacts 52. As themetals 48 and 50 begin to cool, contacts 52 will again close allowingcurrent to flow through indicator lamp 142. The opening and closing ofcontacts 52 which is normally in the range of l to 2 cycles per secondwill cause the indicator lamp 142 to flash. Though not specificallyshown in the figure, it is understood that NOR gate 134 receives voltagefrom the vehicle battery +V whenever the ignition switch 12 is in theSTART or RUN position. Also, wiper arm I16 and 114 have an OFF position(not shown) to prevent the battery voltage +V from being connected towarning indication system 10. The self test through resistor 144 andwiper arm 116 operate as previously mentioned in conjunction with FIG.1.

Referring now to FIG. 3, like components as shown in FIG. 1 will berepresented by the same reference numeral increased by 200. Theessential difference between the embodiment shown in FIG. 3 and theembodiment shown in FIG. 1 resides in the connection of the indicatorlamp 242. In FIG. 1, the lamp 42 was connected directly to the voltagesource +V. However, in FIG. 3 the lamp 242 is connected directly toground. Upon receiving a positive voltage output from AND gate 240, theindicator lamp 242 will glow. Again when an out-of-tolerance conditionexists the multi-vibrator 232 interrupts the output of AND gate 240 toflash the indicator lamp 242 at an approximate rate of l to 2 cycles persecond. Though not shown in FIG. 3, it should be understood thatmulti-vibrator 238, OR gate 234 and AND gate 240 receive their voltagefrom the vehicle battery +V whenever the automotive vehicle ignitionswitch 12 is in the START or RUN position. All voltage is removed whenthe ignition switch 12 is OFF. Also, an automatic test is included byresistor 244 to self test the indicator 242 when the ignition switch 12is in the START position.

Referring now to FIG. 4, wherein like components are represented by thesame reference numerals as the reference numerals used in FIG. 1increased by 300. The indicating lamp 342 is connected to ground thesame as shown in FIG. 3. Hence, when the voltage is applied to the otherside of indicator lamp 342, the lamp will glow warning the vehicleoperator that an out-of-tolerance condition in the braking systemexists. An out-of-tolerance condition sensed by switch 318, 320, 322 or324 will generate a voltage output from OR gate 334. The current outputfrom OR gate 334 will begin to flow through bimetal switch 346, which isthe same as bimetal switch 46 shown in FIG. 2. As described inconjunction with FIG. 2, the current through bimetal switch 346 willcause the two metals 348 and 350 to expand at different rates. Becauseof the different expansion rates of metals 348 and 350, the contact 352will be broken. Because the contact 352 has been broken, current nolonger flows through bimetal switch 346. Subsequently, as the two metals348 and 350 begin to cool, they again resume their normal position toclose contacts 352. The frequency of operation of the bimetal switch 346can be anywhere from between 0.2 to 5 Hertz. Hence, when anout-oftolerance condition that is monitored by the switches 318, 320,322 or 324 exists, the indicator lamp 342 will flash at a rate clearlyvisible by the vehicle operator. Again, as previously described, anautomatic test is included through resistor 344 for testing the brakefailure warning system 310 when the automotive vehicle switch 12 is inthe START position. Though not shown in the drawings, the OR gate 344will receive power from the vehicle battery +V when the ignition is ineither the START or the RUN position.

Though there are many ways of implementing the design as illustrated inthe embodiments shown in FIG. I through 4, the following description ofFIG. 5 will explain in detail one method of implementing the inven--tion. Though functionally FIG. 5 is the same as FIG. l,

u there will be some design changes concerning the incorporation of theelectronic control unit switch 24. When possible, the same referencenumerals in FIG. 1 will be used in FIG. 5. The essential differencebetween FIG. 1, which is one of the simplest possible designs, and theschematic of FIG. 5 resides in the construction of OR GATE 34 andinverter 36. The OR gate 34 and inverter 36 have been replaced with aNOR gate 35 and an inverter 37 (not shown in logic form) for the outputthereof. The switches 22, 18 and 20 provide the ground inputs for theNOR gate which is inverted by inverter 37 to provide the same functionas OR gate 34 of FIG. 1. Switch 24 is not connected to NOR gate 35 orinverter 37. Instead, it bypasses this part of the circuit as will besubsequently described. The reason for going to this type ofconfiguration is because the fluid-level switches are, in thisparticular case, of the carbon type. Because the resistance of carbon isin the semiconductor group, and the resistance of the brake fluid variesover a wide range, a NOR gate 35 is needed to detect when a fairly largevalued resistance becomes essentially infinite.

The vehicle battery +V is fed in through double pole, double throwignition switch 12 to wiper arm 14, and 16 to supply power to the brakefailure warning system 10. Notice that when the ignition switch is ineither the START or the RUN position +V is connected to indicator lamp42 and the voltage bus 54.

Starting first with the pressure differential switch 22, it is connectedin series between a ground bus 56 and voltage dividing resistors 58 and60, with the connection between the resistors 58 and 60 being connectedto the base of NOR gate transistor 62. The emitter of transistor, 62 isconnected to the junction of voltage dividing resistors 64 and 66 thatare connected between the voltage bus 54 and the ground bus 56. Hence,the emitter of transistor 62 is at some voltage potential. As long asthe base of transistor 62 is at some voltage potential lower .than theemitter, then the transistor will not conduct so that thecollector-toemitter voltage is high. If the switch 22 should open dueAlso, combining with transistor 62 to form a NOR gate are transistors 68and 70 wherein fluid level switches 18 and 20 are both connected on oneside to ground bus 56. The other sides of fluid level switches 18 and 20are connected to the bases of transistors 68 and 70 and throughresistors 72 and 74, respectively, to the voltage bus 54. The emittersof transistors 68 and 70 are normally at a higher voltage potential thanthe bases of the transistors as provided by voltage dividing resistors64 and 66. Because fluid level switches 18 and 20 tend to vary inresistance as the resistance of brake fluid varies over extendedresistance values, the ratio of resistor 66 to resistor 64 must berather large to set emitter bias of transistors 62, 63 and 70. Assumethat fluid level switch 18 is opened because of a low fluid level in thebraking system. Then because the full amount of the voltage bus 54through resistor 72 is developed on the base of transistor 68, thetransistor will conduct thereby developing a voltage potential acrossresistor 78. Likewise, if fluid level switch 20 should open, transistor70 will conduct causing a voltage potential across resistor 78. Sincethe collectors and emitters of transistors 62, 68 and 70 are all common,the conduction of any one of these transistors causes voltage potentialto be developed across resistor 78 to the base of transistor 76. Sincetransistor 76 is at PNP transistor wherein the previously describedtransistor 62, 68 and 70 are NPN transistors, if the base of the PNPtransistor 76 is of a sufficiently lower voltage potential than theemitter, then transistor 76 will conduct and the collector of thetransistor 76 will have a high voltage potential.

The collector of transistor 76 is connected through resistor 80 to thebase of NAND gate transistor 82. Transistor 82 is connected in serieswith NAND gate transistor '84 so that if the positive voltage signal isreceived at'the base of both transistors, then they will begin toconduct. When the NAND gate transistors 82 and 84 conduct, the currentsupplied through indicator lamp 42 to the ground bus 56 will cause theindicator lamp 42 to light up. The input to the base of transistor 84,as will be subsequently described, is the output from themulti-vibrator. Notice that transistor 82, which forms one half of aNAND gate circuit with transistor 84, can be bypassed if a ground isapplied by the adaptive braking control unit which thereby indicates anadaptive braking failure. The ground is supplied by switch 24 whichleaves the NAND gate as a one input gate.

At this point it should be noted that if one of the switches 18, 20 or22 should open or a ground is applied from the adaptive braking controlunit, then the indicator light 42 will flash at a rate determined by theinput from the multi-vibrator to NAND gate transistor 84. It should beobvious to those skilled in the art that numerous other functions couldbe monitored by the inclusion of additional OR or NOR gate transistorsor the providing of other sources of ground to the indicator lamp 42.Also by the periodic interruption of the current carrying path suppliedto indicator lamp 42, the lamp will flash.

Briefly mentioning the multi-vibrator 38, when the voltage bus 54 isenergized, one of the multi-vibrator transistors 86 or 88 will start toconduct. After a given time period the transistor will stop conductingand the other transistor will start conducting. The design of themulti-vibrator 38, which is well known to those skilled in the art,includes appropriate valves of resistors 94, 96, 98 and 100 andcapacitors 90 and 92 to determine the length of time the transistors 86and 88 will alternately conduct. The alternate conduction of transistors86 and 88 determine the frequency of operation of the lamp 42.

For coupling purposes, transistor 86 is connected through resistor 104to the base of transistor 102 so that a positive voltage on thecollector of transistor 86 when it is non-conducting will stop theconduction of transistor 102. When transistor 102 is conducting, thecollector current flows through resistor 106 to the base of AND gatetransistor 84 to get the multi-vibrator input to flash indicator lamp 42as previously described.

Diode 108 is used to prevent negative voltage spikes on the voltage bus54 from causing damage to the circuit. Also, resistor 44 which isconnected to the base of transistor 62 provides an automatic test whenwiper arm 16 of the ignition switch is in the START position. Resistor44 could have been connected to the base of transistor 68 or 70. Diode109 is used to prevent current flow through resistors 58 and 44 andstarter solenoid coil (not shown) to ground.

it should be obvious to those skilled in the art that the resistortransistor logic could be replaced by diodetransistor logic or relaylogic. Though only four embodiments were shown in FIGS. 1 through 4, andone in specific detail in FIG. 5, it should be obvious to those skilledin the art that many other combinations are possible. The AND-OR logiccould be replaced with NAND-NOR logic or .combinations thereof. Also,many other parameters not necessarily associated with the braking systemcould be monitored.

lCLAlM:

l. A vehicle malfunction indicator system comprisa plurality of sensors,each of said sensors being adapted to detect a malfunction in acomponent of the vehicle;

an indicating device;

first gating means having an output and a plurality of inputs, each ofsaid inputs being connected to a different one of said sensors, saidfirst gating means producing an output signal whenever any of thesensors connected to any ofits inputs produces an output signal;

second gating means having an output connected to said indicating deviceand a pair of inputs, one of said inputs being connected to the outputof said first gating means; and

pulse generating means connected to the other input of said secondgating means, whereupon the latter produces a pulsating output signalwhen said first gating means produces an output signal, thereby causingpulsating actuation of said indicating device when any of said sensorssenses a malfunction.

2. The invention of claim 1:

said pulse generating means including multi-vibrator means having afrequency output between 0.2 and 5 Hertz;

said second gating means being an AND gate.

3. The inventionpf claim 1; said vehicle having a starting switch forstarting the vehicles engine; and means transmitting a signal to one ofthe inputs of said first gating means when said starting switch isactuated whereby said indicating device is actuated whenever the engineof the vehicle is started.

1. A vehicle malfunction indicator system comprising: a plurality ofsensors, each of said sensors being adapted to detect a malfunction in acomponent of the vehicle; an indicating device; first gating meanshaving an output and a plurality of inputs, each of said inputs beingconnected to a different one of said sensors, said first gating meansproducing an output signal whenever any of the sensors connected to anyof its inputs produces an output signal; second gAting means having anoutput connected to said indicating device and a pair of inputs, one ofsaid inputs being connected to the output of said first gating means;and pulse generating means connected to the other input of said secondgating means, whereupon the latter produces a pulsating output signalwhen said first gating means produces an output signal, thereby causingpulsating actuation of said indicating device when any of said sensorssenses a malfunction.
 2. The invention of claim 1: said pulse generatingmeans including multi-vibrator means having a frequency output between0.2 and 5 Hertz; said second gating means being an AND gate.
 3. Theinvention of claim 1: said vehicle having a starting switch for startingthe vehicle''s engine; and means transmitting a signal to one of theinputs of said first gating means when said starting switch is actuatedwhereby said indicating device is actuated whenever the engine of thevehicle is started.